Program transmission over wires



1,628 697 May 1927' J. F. TOOMEY PROGRAM TRANSMISSION OVER WIRES Original Filed Nov. 11, 1922 l g I L w 1570319621 IN VEN TOR A TTORNEY Patented May 17,1927.

UNITED STATES PATENT OFFICE.

JOHN F TOOMEY, OF NEW YORK, N. Y., ASSIGNOR T0 AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

PROGRAM TRANSMISSION OVER WIRES.

original application filed November 11, 1922, Serial No. 600,857, Patent No. 1,591,108. Divided and this application filed January 18, 1924. Serial No. 687,1QO.

This invention relates to systems of communication and more particularly to systems for disseminating news, information, music or the like. This application is a division of application Serial No. 600,357, filed November 11, 1922. Patent Number 1,591,108.

Various schemes have been proposed heretofore for program transmission purposes. The only one of these schemes which has been exploited to any extent is radio broadcasting, that is, the transmission of news, information or entertainment by means of radio telephone equipment so that persons provided with suitable radio receiving sets tuned to the proper wave length may receive the distributed entertainment or the like. 7

This'method, however, has very serious objections. In the first place, numerous broadcasting stations in the same area opcrate on wave lengths sufiiciently close together to interfere with each other. Furthermore, radio telephonic transmission necessarily involves the use of a much wider band of the frequency spectrum than is used for wireless telegraph purposes, and in view of the fact that the number of wave lengths available for radio communication are necessarily limited it is undesirable that wave lengths necessary for commercial communication should be utilized for purposes of more entertainment. Finall in order to avail himself of the distribute information or entertainment, each individual subscriber must provide himself with a radio receiving equipment which involves storing upon his premises extensive storage batteries which are constantly in need of re-charging, togather with a considerable amount of delicate and elaborate electrical apparatus, such as coils. detectors, amplifiers, etc., all of which involve careful maintenance. Moreover, the radio receiving set as now known is. at its best, an inherently ugly thing, absolutely out of place in the home and re uir ing for its operation a network of unsig itly wiring.

Realizing the inherent limitations of radio broadm-isting, proposals have been made to use existing wire systems, such as telephone, telegraph or power networks for program transmission purposes by transmitting carrier frequencies over such existing power or mmmunication lines. Such a method, however, would be extremely expensive as well as complicated, as it involves a Very consid= erable reorganization of the telephone plant or power plant, and requires the use of quite complicated and expensive apparatus.

The ordinary telephone plant, however, offers unusual facilities for program transmission purposes by the use of ordinary telephonic methods and without the emplo ment of any high frequency or carrier motilods of signaling. When it is realized that the average subscribers telephone set is in use for telephonic purposes only during an extremely small part of the time it becomes at once apparent that if the telephone line, during its idle periods, could be used for transmitting news, information or e tertainment, the plant could be used 1 uch more economically and the information orthe like distributed could be transmitted to the subscriber in the simplest manner possible. It may further be observed that the average subscriber to a program service, particularly a service for transmitting entertainment, would only desire to avail him self of the service during the late afternoon or during the evening, at which times the average subscribers telephone is only used 'for social purposes and is rarely or never used for business calls.

Having these circumstances in mind, it is proposed by this invention to provide simple, practical and economical arrangements by which news, information, music or other forms of entertainment may be transmitted at ordinary telephonic frequencies from a central program station over subscribers telephone lines. It is also proposed by this invention to provide a system whereby the telephone subscriber may receive the program service without interfering in any way with the use of his line for ordinary telephone purposes. This invention also renders available a program distributing system. in which the apparatus, not only at the central station but more particularly at the subscribers station, will be extremely simple and economical and yet efficient.

The invention may now be more fully' understood by reference to the following detailed description thereof when read in connection with the accompanying drawing, in which Figure 1 is a circuit arrangement illustrating one embodiment of the invention and Fig. 2 is a circuit arrangement illustrating a similar embodiment provided with an amplifying device for the loud speaker at the receiving station.

Referring to Fig. 1, L designates an ordinary subscribers line to which program service is normally connected through the back contacts of a cut-oil relay COR. The equipment associated with the subscribers line at the switchboard, such as the answering jack J and the multiple jacks J, J, etc, is normally disconnected from the line at the contacts of the cut-off relay, this an rangement of the circuit operating to eliminate the cross -talk interference which might occur between adjacent circuits in the switchboard cable. A line relay LR is provided, this line relay being associated with the portion of the circuit extending from the line L to the program station instead of being associated with the part of the circuit extending to the answering jack. The cutoff relay COR is arranged to be operated over the sleeve circuit of the answering jack whenever the plug of a cord circuit is inserted in said jack. The cut-off relay, when actuated, disconnects the program equipment and hence the line relay LR from the line so that it will be apparent that incoming calls to the subscriber may be completed in the usual manner.

The program equipment comprises a trunk T, leading to a program station (not shown). .An amplifier 25 is associated with the trunk T through patching jacks J, for amplifying the program currents to the desired am litude for transmission over the lines of t e group to which the line L belongs. In this connection, it will be noted that subscriberslines having similar impedance characteristics may be grou ed together and associated by means 0 jacks, such as the 'ack J to common bus-bars connected' to t e output of an amplifier, such as 25. The amplifier may be so adjusted as to amplif the currents to the desired value for all 0 the lines of the group. For example, lines in the same cable having approximately the same length, the same gauge conductors and approximately the same capacity, would all be grouped on certain bus-bars. The amplifier, such as 25 at the central office, associated with this group of lines, would be equipped with the proper type of output coils and other apparatus so that it would work at its maximum efiiciency when connected to its associated group of lines. Means may also be provided when necessary for equalizing the transmission over the various groups of subscribers lines. The arrangement illustrated is designed on the assumption that a fixed program will be given at certain hours and consequently a key K is provided for switching the rogram station into connection with the usbars associated with a group of Subscribers lines. This key will be actuated during such periods as programs are being rendered. At other periods, the key will be in its normal position and its contacts are so arranged that when the key is normal, the

bus-bars 26 are short-circuited. This prevents the possibility of subscribers connected to the same bus-bars conversing with each other over the common connection when the program station is not connected.

\Vhen the key K is actuated a busy tone is applied to the sleeve of the answering jack J and its multiples through an extra winding on the cut-off relay COR to indicate to the operator that the program service is being applied to the line.

The jack J is provided for the purpose of disconnecting any given line, such as L, from its normal group and patching it into connection with some other program circuit or group. For this purpose the patching cord may be connected to a multiple (not shown) of the jack J 3 of the other program circuit. The patching jacks J and J 3 are provided for patching in different amplifiers or for connecting the bus-bars 26 with different program stations. By this arrangement a program of one character may be connected to one group oflines and a program of different character to another group of lines. The jacks, however, enable the programs to be switched from group to group, as the exigencies of the service may require. The jack J on the other hand, permits the connection of a subscriber, normally' in a given group receiving a certain program, to the bus-bars of another group receiving a different program which 'he may at that particular time prefer to hear.

The apparatus at the subscribers station A is extremely simple, consisting merely of the standard substation set 10 and a loud speaker 11, the latter being connected through a transformer 14 to a circuit bridged across the line through a key K and a back contact on the switchhook of the substation set. When the receiver is on the switchhook and the contact of the key K is closed, the program applied to the bus-bars 26 will be transmitted over the line L and actuate the loud speaker 11. The program may be applied to the subscribers line during a given period whether the subscriber desires it or not. If the subscriber does not care to hear the program he will simply maintain the contact of the key K open and if he does desire to hear the program he may do so by closing the contact of the key. During the rendition of the program, a busy tone is applied over the upper contact of the key K at the central oflice, over the lower back contact of the cut-ofi' relay and through" the lower winding of the cut-off relay to ground. The inductive action between the two windings of the cut-oil relay meeseee transmits e busy tone to fine sleeve conductor of the answering jack.

If a call should come in for the iine L while the program is being; rendereci, ihe operator may disregard the busy tone and insert the plug P of the usnei oonneciing: word into the answering jack J, or one of he muitipies thereof, thereby energizing the cut-011 113i? through its upper Winding. The out-off relay at once disconnects the line L from the circuitineinding the iine relay LR, transformer 2?, jack 5,, leads 28, key K, amplifier 26 emi trunk T lending to i116 program station. The subscriber, upon being rung, removes his receiver irom the switchiiook, thereby disconnecting the loud speaker 11 and connecting the teiephone set into circuit with the iine L. Upon henging up the receiver at the end of the conversation, the iond speaker will again he conneeied into circuit and as soon as the eonnec tion is taken down at the centre oiiice by Withdrawing the ping P, the cut-off reiay "will be deenergized and the circuit resiored to the program transmitting condition.

if, While the line is being used for program receiving, the subscriber desires i1) make e eeli, he may do so by simpiy removing the reeeiver from the switchhook, Whieii disconnects the loud speaker 11 from the iine and at the same time connects iiie so? seribers set into the circuit. The reiey LE, wiiieii is included in she program eoniiection, win he energized; and compieie a circuit for the line imnp 15 The operator, upon observing the glowing of the iamp, will insert the plug P of a eord in ens-Werine" "aci: thereb ener izin Y the enter reiey m disconnect the line L from the pro gram circuitand to conneet it to the enswer-' ing jack Restoration of the cireui'b to the program transmitting eondision at the end of she conversation wiii he as previonsiy de scribed,

Fig. 2 iiinsisraiee e eireuifi similar to tiizub shown in F i. In this srrangemeni, how ever, iiie substation equipped Wieii e vacuum tube amplifier 32 in eddi'hion to he 30nd speaker 11, In order to avoid the ineieiiaiion of batteries at the subscribers station, the eircui, 3* so arranged that the for operating die plate anci the iiiee nient circuits of the empiiiier is iirmishmi over sine line from iiie central ofiiee. The phase current may be furnished from a 48- \Oiil battery, for exampie, through the winci ing oi. the marginal iine reiey LE over the ring side of the line, The filament current, on him oiiier band, may be supplied from s 10-voit battery over the tip side of the iine. Since the "telephone iine may act as so onienne'and pick up transmission from e raciio station, the subscriber might use the empiiiier and 20116. speaker eo ietect the radio transmission at such times as the centrei "understood i1 er-zillion, which is eiiioscriiiers program noiiririctio d oroier to prevent em, as switch Yideei 3% the cenirei office "for ciisei Bing the current suppiy circuit of ihe empiifier, whiie at the same time providing the usual direct currentsuppi v for the teiepiione substetionequipment.

in the circnio of F 2, as Weii es in Fig. 1, the iine is normeiiy eonnecied to eiie program circuit 28 over the contacts of the cue oii relay, so iiisa the subscriber, in orcier to ob min the program transmission, merely throws the key K at the substation, thereby cone piezing connection to the input transformer 34% of tile empiifier 42 and at the some time completing; the fiizimene and plate circuit, of tine enipiiiier. ii iien she eenfiroi program equipment is operating, end the iine L is; iiieconnecteii om the program trunk and eonnecteri to the switching jack J for the purpose oi esiebiishing e teiephone conneoi-ion, a network N may be connected to the program trunk The neiwork li' simulates the impedance of the line and thereby mainreins consienithe impedance of the network of eircni os suppiieci from the program trunk. Iii this arrangement were noiprovidedl 12111 e meteriei number of me iines snppiieci from the same pro-gram cireeifi were simuiesneoiisiy "eseci ifor teiephonie purposes, the profnreooniiesion to the remaining iines would Toe gree'iciy itriereeeeoi Perisher ciei ie of iiie inveniion 1'. she ciescripii .11 oi he opfoiior's: Where eke proeopiiei to the iins L over the circuit ough Liie over the noerr eon iecte the cutoff reiey CUR rough the transformer 9/8, See swiiicii Wlii he connect the i-Zi-voi'e i i ery the onsioer 3% and the lG-Voii L eeery io he bus-"oer Cnrreni; enp T CiTGLiiiZS for the empiiiiers oLi eii i L es connected to the busimrs end 31 Wiii shes proviciecl The sub soriioer may now e'veii iiimseif of this service by aceneizing e K. This oioses the l nens eireoi rem the i8-voii be r31 over conteci: oi the ke ionsii)E'30,ii'iY-fl H the Winciing of relay LE, over the ermatiire of the cut- 0E eeiey GCPR, over the ring coniiiictor oi the iine, back coniec of the SWii/iiiiii0 2-i oi the ii ieift-iizmri make contact of the key K, enci iiirougii the retard coii to iiie pieie of the empiifier 42. The line reiay L3; is merginei and not actuated by the email current flowing through the high impedenee of the piei'e cirenit. The fiiament circuit ie compieieei from the iQ-voit batmey be gram service is o i re upper :r

rery, over the iower make contact of the key iii? 42 to ground. The amplifier is now energized and amplifies the program current transmitted over the line to the loud speaker 11.

If while the circuit is in this condition the subscriber wishes to initiate a call, the receiver is removed from the hook, thereby opening the bridge including the input transformer 34 of the amplifier 42 and also opening the battery supply circuit for the plate of the amplifier, so that the amplifier and loud speaker cease to function. A low impedance path is at the same time closed over the line L through the subscribers set 10 as follows: from the 48volt battery, over the bus-bar 30, through the winding of the marginal relay LR, over the ring side of the line, over the subscribers switchhook,

through the subscribers set 10, back over the,

tip side of the line L and over the bus-bar Ill to the 10-volt filament battery. The two batteries are now connected in series through the low impedance of the subscribers set 10 and the current flow is sufficient to operate the marginal line relay LR which causes the line lamp 15 to glow. The operator is thus informed that a connection is desired and plugs into the jack J, whereby the cut-off relay COR is actuated. The cutoff relay COR, upon attracting its armature; 32 and 34, disconnects the line L from the program trunk and connects itto the tip and ring conductors of the jack J. At its armature '35, the cut-off relay opens the circuit of the line lamp 15 and at its armature 36 the cut-off relay substitutes the network or resistance N for the line L, thereby maintaining the impedance looking through the transformer 27 from the program circuit sub: tantially the same as when the line L is connezted to the transformer.

At the end of the conversation the subscribcr hangs up his receiver. The operator. upon receiving the disconnect signal, withdraws the plug from the jack J, thereby deenergizing the cut-off relay COR. As a consequence, the line L is again connected to the program circuit, and if the key K has remained actuated, the subscriber will reccive the transmission as before.

If a call comes in for the line L the operator may, by inserting the plug of the connecting cord into the jack J. energize the cut-off relay, which at once disconnects the line L from the program circuit and connects it to the jack J as before. The current supply circuit for the amplifier 42 will be opened by the arniatures 32 and 34 of the cut-off relay, so that. the amplifier and loud speaker at the subscribens station will be inoperative. Upon the subscriber receiving the ringing signal, he will remove the receiver from the switchhook and the telephone conversation may take place in the usual manner. it the conclusion of the conversation the circuits may be restored to the program condition as previously described.

When the program apparatus at the central station is not functioning, the key K will be restored to normal, thereby disconnecting the 48-volt battery and the 10-volt battery from the ring and tip sides, respectively, of the various lines. The ring side of the lines will be connected over the normal contact of the key K to the usual 24- volt battery and the tip sides of the line; will be grounded over the normal contact of the key K Under this condition the line relay LR will respond to the operation of the switchhook in the usual manner, so that telephone connections may take place. The amplifier 42, associated with the loud speaker set, will be rendered inoperative, however, and thus effectually prevent the subicriber from using the amplifier and loud speaker to receive radio transmission which might be picked up by the line L acting as an antenna.

It will be obvious that the general principles herein disclosed may be embodied in other and different organizations widely different from those illustrated without departing from the spirit and scope of the appended claims.

\Vhat is claimed is:

1. In a telephone system, a telephone line terminating at a subscribers station at one end and a central office at the other end, a line relay associated with said line at the central ofiice', a telephone set at said subscribers station, means to supply the energizing current for the transmitter of said set from the central office through said line relay, switching means at the central olfice for interconnecting said line with other telephone, lines for ordinary telephonic intercommunication, a special receiving arrangement at said subscribers station for receiving program transmission, a program transmitting station, means to connect said special receiving arrangement and said program station with the line when it is not being ,used for ordinary telephone purposes, said special receiving arrangement including an amplifier, and means for supplying an energizing current for said amplifier over said telephone line and through said line relay from the. central office without operating said line relay.

In a telephone system, a telephone line terminating at a subscribers station at one end and a central office at the other end. a line relay associated with said line at the central ofiice. a telephone set at said subsi-ribers station, means to supply the encrgizing current for the transmitter of said set from the central ofiice through said line relay, switching means at the central office for interconnecting said line with other telephone lines for ordinary telephonic interlit) communication, a special receiving arrangement at said subscribers station for receiving program transmission, a program transmitting station, means to connect said special receiving arrangement and said program station with the line when it is not being used for ordinary telephone purposes, said special receiving arrangement including a vacuum tube amplifier, and means for supplying the plate currents to said vacuum tube amplifier over said telephone lines and through said line relay from the central oftice without operating said line relay.

3. In a telephone system. a telephone line terminating at a subscriber's station at one end and a central office at the other end, a telephone set at said subscribers station, switching means at the central otiice for interconnecting said line with other telephone lines for ordinary telephonic interconnnunication, a special receiving arrangement at said subscribers station for receiving program transmission, a program transmitting station, means to connect said special receiving arrangement and said program station with the line when it is not being used for ordinary telephone purposes, said special receiving arrangement including a vacuum tube amplifier, means for supplying the plate and filament current to said vacuum tube amplifier over said telephone line from the central otfice, and means whereby when said subscribers set is used for ordinary telephone purposes energiaing current for said vacuum tube amplifier will be disconnected from the line.

4. In a telephone system, a telephone line terminating at a subscribers station at one end and a central ofiice at the other end, a telephone set at said subscribers station, switching means at the central ofiice for in terconnecting said line with other telephone lines for ordinary telephonic intercommunication, a special receiving arrangement at said subscribers station for receiving program transmission, a program transmitting station, means to connect said special receiving arrangement and said program station with the line When it is not being used for ordinary telephone purposes, said special receiving arrangement including a vacuum tube amplifier, and means for transmitting the filament energizing current of said vacuum tube over one side of the line from the central otfice and the plate current of said vacuum tube over the other side of the line from said central ofiice.

5; In a telephone system, a telephone line terminating at a subscribers station at one nd and a central oflice at the other end, a telephone set at said subscribers station, switching means at the central ofiice for interconnecting said line with other telephone lines for ordinary telephonic interco-mmunication, a special receiving arrangement at said subscribers station for receiving program transmission, a program transmitting stat on, means to connect said special receiving arrangement and said program station with the line when it is not being used for ordinary telephone purposes, said special receiving arrangement including a vacuum tube amplifier, means for supplying the plate and filament currents to said vacuum tube amplifier over said telephone line from the central otfice, and means whereby when said subscrilfiers set is used for ordinary telephonic purposes said plate and filament currents will be disconnected from the line.

6. In a telephone system, a telephone line terminating at a subscribers station at one end and a central o'tiice at the other end, a telephone set at said subscribers station, switching means at the central otlice for interconnecting said line with other telephone lines for ordinary telephonic intercommunication, a special receiving arrangement at said subscribers station for receiving program transmission, a program transmitting station, means to connect said special receiving arrangement and said program station with the line when it is not being used for ordinary telephone purposes, said special receiving arrangement including an amplifier, means to supply the energizing currents for said amplifier over said telephone line from the central ofiice, and means at the central otfice for disconnecting the energizing circuit of the amplifier without disabling the telephone line for telephone purposes.

7. In a telephone system, atelephone line terminating at a subscribers station at one end and a central ofiice at the other end, a telephone set at said subscribers station, switching means at the central oiiice for interconnecting said line with other telephone lines for ordinary telephonic intercommunication, a special receiving arrangement at said subscribers station for receiving program transmission, a program transmitting station, means to connect said special receiving arrangement and said program station with the line when it is, not being used for ordinary telepl one purposes, said special receiving arrangement including a vacuum tube amplifier, means for supplying the plate and filament currents to said vacuum tube amplifier over said telephone line from the central otiice, and means for disconnecting the curgent supply for the plate and filament circuits of said vacuum tube amplifier without disabling the telephone line for ordinary telephone purposes.

In testimony whereof, I have signed my name to this specification this 14th day of January, 1924.

JOHN F. TOOMEY.

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